Feature request: Ring terminal bell on Pomodoro completion

[mstfacmly]

Just a small feature request, but it's easy to lose track of the Pomodoro timer if we don't keep an eye on the terminal. Having a bell ring on completion would help keep track of the elapsed time.

• Node Version: v6.11.4
• tiny-core-terminal version: 1.3.2
• Shell: bash/dash
• Terminal Program: GNOME terminal
• Operating System: Linux (Ubuntu 17.10)

Thank you!

[mojoaxel]

According to the node-notifier docs the current implementation (L355 and L366) only works on macOS 10.9.
I think node-notifiershould be exchanged for something more platform independent.